Increased calcium permeability is not responsible for the rapid lethal effects of amphotericin B on Leishmania sp.
The mode of action of the polyene antibiotic amphotericin B (AmB), the drug of choice for the treatment of systemic fungal infections and visceral leishmaniasis, is still unclear. An increase in intracellular Ca2+ concentration [( Ca2+]i), toxic in many cases, has been postulated as a possible lethal mechanism for AmB. Cell permeabilization to ethidium bromide (EB) was used as a criterion of viability. Kinetics of the DNA-EB fluorescent complex formation was studied in ergosterol-containing Leishmania promastigotes. Intracellular Ca2+ concentration was measured using quin-2 fluorescence in parallel aliquots. It is shown in this work that AmB can act as an efficient Ca2+ ionophore. However, the rapid permeabilization effect induced by AmB on these cells was not dependent on an increase in [Ca2+]i. On the contrary, it was found that leishmanicidal effect of AmB was enhanced in the absence of external calcium. Furthermore, A23187 a Ca2+ ionophore did not provoke cell permeabilization to EB.
Cohen
B E
BE
Centro de Biología Celular, Facultad de Ciencias, Universidad Central de Venezuela, Caracas.
Benaim
G
G
Ruiz
M C
MC
Michelangeli
F
F
D000666:Amphotericin B / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D007700:Kinetics; D007891:Leishmania / Q000187:drug effects*; D007892:Leishmania braziliensis / Q000187:drug effects* / Q000378:metabolism
D000666:Amphotericin B; D002118:Calcium